1. Field
The present disclosure relates to zoom lens systems, interchangeable lens apparatuses, and camera systems.
2. Description of the Related Art
In recent years, interchangeable-lens type digital camera systems (also referred to simply as “camera systems”, hereinafter) have been spreading rapidly. Such interchangeable-lens type digital camera systems realize: taking of high-sensitive and high-quality images; high-speed focusing and high-speed image processing after image taking; and easy replacement of an interchangeable lens apparatus in accordance with a desired scene. Meanwhile, an interchangeable lens apparatus having a zoom lens system that forms an optical image with variable magnification is popular because it allows free change of focal length without the necessity of lens replacement.
Zoom lens systems having excellent optical performance from a wide-angle limit to a telephoto limit have been desired as zoom lens systems to be used in interchangeable lens apparatuses. Various kinds of zoom lens systems each having a negative lens unit located closest to an object side, and a multiple-unit construction have been proposed.
Japanese Laid-Open Patent Publication No. 2007-078834 discloses a zoom lens having a four-unit construction of negative, positive, negative, and positive, wherein the second lens unit has a second-A lens element composed of one positive lens, and a second-B lens element which is composed of a negative lens and a positive lens and which has positive refractive power, and wherein the second-A lens element moves in a direction perpendicular to an optical axis.
Japanese Patent No. 3486532 discloses a zoom lens having a four-unit construction of negative, positive, positive, and positive, or negative, positive, positive, and negative, wherein the third lens unit comprises a cemented lens composed of a negative lens and a positive lens, or a cemented lens composed of a positive lens and a negative lens, and wherein the third lens unit moves in a direction nearly perpendicular to an optical axis to perform blur compensation.
Japanese Patent No. 3587272 discloses a zoom lens having a two-unit construction of negative and positive, wherein the second lens unit has a second front lens unit having positive refractive power and a second rear lens unit having positive refractive power, and wherein only the second front lens unit moves to an image side to perform focusing.